Basic refrigeration systems cool a target fluid circulating through an evaporator where the latent heat of vaporization of a working fluid is obtained from the sensible heat of the target fluid, thereby reducing the temperature of the target fluid. In order for the working fluid to evaporate, the working fluid must first be in a liquid state at a pressure below the vapor pressure of the working fluid. In typical refrigeration cycles, this liquid state is obtained by compressing the working fluid to a high pressure and temperature, rejecting the thermal energy to the environment either by conduction or convection, and then passing the working fluid through a throttling valve to reduce the pressure of the working fluid in an isenthalpic expansion. The resulting liquid working fluid is then evaporated in the evaporator by absorbing thermal energy from the target fluid. The evaporated working fluid is then returned to the compressor to complete the cycle.
One disadvantage to this type of refrigeration system is that the compression system requires power in the form of expensive mechanical energy. An alternate way of compressing the working fluid is through the use of an ejector which uses a high pressure and temperature motive fluid to entrain the working fluid (e.g., a suction fluid) after the working fluid has been discharged from the evaporator. The fluid mixture discharged from the ejector follows the conventional refrigeration cycle before being re-entrained into the ejector by additional, high temperature motive fluid.
Although there are several types of refrigeration cycles that employ ejectors, it nonetheless remains desirable to find improved refrigeration cycles in varying thermodynamic applications that offer improved efficiency and reduction in production costs.